Relational Calculcus

Question 1

SELECT

Answer 1

σ (select condition) R

Unary operation
Applies to rows
Commutative

Question 2

PROJECT

Answer 2

π (attribute list) R

Unary operation
Applies to columns
Removes duplicate tuples

Question 3

RENAME

Answer 3

ρ (new attribute names) (R)

Applies to tables and columns

Question 4

UNION

Answer 4

R ∪ S

Result is all tuples that are either in R, in S or in both.
Duplicate tuples are eliminated.

Question 5

INTERSECTION

Answer 5

R ∩ S

Result is rows that are in R and in S

Question 6

SET DIFFERENCE

Answer 6

R - S

Result is rows that are in R, but not in S
Not commutative

Question 7

CROSS JOIN (also called Cartesian Product)

Answer 7

R x S

Combines every tuple from one set with every tuple from another (Total number of tuples should be # in R * # in S)

Question 8

JOIN

Answer 8

R ⋈ S

Combines two related tuples into one big tuple

Question 9

θ JOIN

Answer 9

θ = any conditional operator

Excludes NULL or any result where θ isn’t true

Question 10

EQUIJOIN

Answer 10

Uses = operator

Question 11

NATURAL JOIN

Answer 11

Same as EQUIJOIN if all columns share the same names

Removes duplicate column names

Question 12

OUTER UNION

Answer 12

Allows union of two relations that are not union compatible

Question 13

LEFT OUTER JOIN

Answer 13

Keeps every tuple on the left, but fills in matches on right where applicable. No matches are padded with NULLs

Question 14

RIGHT OUTER JOIN

Answer 14

Keeps every tuple on the right, but fills in matches on the left where applicable. No matches are padded with NULLs

Question 15

FULL OUTER JOIN

Answer 15

Keeps all tuples on both sides, even if they don’t match

Question 16

INNER JOIN

Answer 16

Tuples that do not match the criteria are not displayed